About the origin of the 0.15 to 0.20 eV defect level in cadmium telluride

The exact origin of the defect levels present in cadmium telluride in the 0.15 to 0.20 eV energy band is under discussion since the beginning of the microscopic characterization of this II–VI semiconductor. Physical defects, residual chemical impurities, and complexes have been successively considered. In this paper, the results are presented of investigations on a large number of crystals grown by THM which are characterized both, by thermally stimulated current (TSC) and photoinduced current transient spectroscopy (PICTS). These materials are grown either undoped, chlorine and copper doped, and some are irradiated by a strong γ-ray source. The concentration of chemical residuals is determined in each case by atomic absorption measurements. It appears that the defects origin is more complicated than generally considered, as will be discussed.